This is a competing renewal of a multi-year conference grant that has supported a forum for researchers to pursue collaborative studies of the molecular genetics of obsessive compulsive disorder (OCD). This application is consistent with NIMH initiatives to facilitate meetings in which researchers come together to establish mechanisms for collaborating in a manner that would facilitate the detection of genes predisposing to psychiatric disorders. At the present time, there are approximately 60 researchers who have attended the meetings of this group. These individuals come from 38 different research centers in 13 foreign countries and the United States. OCD is a serious psychiatric condition that can have debilitating affects on both adults and children. The importance of genetic factors in OCD has been demonstrated by twin and family aggregation studies. Furthermore, recent molecular genetic studies have begun to provide evidence that specific genes may play a role in the manifestation of the disorder. Although these preliminary results are encouraging, several considerations suggest that fully clarifying the genetic architecture of OCD will require large samples and collaborative efforts. It is clear from ongoing studies of the genetics of schizophrenia, autism, Gilles de la Tourette's syndrome, ADHD and bipolar disorder that are consistent with statistical considerations regarding the power to locate genes for complex disorders, that samples collected by individual investigators may not be sufficiently large to provide significant evidence for genetic linkage. Furthermore, once linkage has been demonstrated, even larger samples sizes are needed to identify and characterize susceptibility genes. Thus, it is clear that coordinated collaboration is needed to share findings and pool samples. Cooperative research of this type is often difficult. With the support of the Obsessive Compulsive Foundation and this grant from NIMH, this group of investigators is collaborating on the first Genome Wide Association Study of OCD. At the present time, investigators from 19 different sites have agreed to combine their OCD samples. The total sample consists of approximately 4,500 individuals, 1,800 singleton cases and 800 triads consisting of an affected individual and two parents. It is expected that the results of this GWAS will be published before December 2008. Thus, the aim of this proposal is to obtain funding that will allow this group to continue meeting to further establish collaborative working groups focused on different aspects of the genetics of OCD. This is a competing continuation application of a meeting grant that has funded meetings of the Obsessive Compulsive Foundation Genetics Collaborative (OCFGC) over the last four years. The major goal of the OCFGC is to develop collaborative studies of the molecular genetics of obsessive- compulsive disorder. Over the last 2 years, the OCFGC has undertaken a Whole Genome Association Study for OCD that should identify susceptibility genes for this disorder.